Catalytic hydration of nitriles

ABSTRACT

A catalytic process for hydration of a nitrile, e.g. acrylonitrile, with water in presence of a manganese dioxide catalyst is operated to obtain improved conversion and longer catalyst life by carrying out the reaction in dilute aqueous solution of a strong acid, e.g. in aqueous solution of HNO3 or HCl at pH below 3.0. The product is the amide, e.g. acrylamide.

United States Patent Fine et al.

[451 Oct. 17, 1972 CATALYTIC HYDRATION OF NITRILES Inventors: Leonard Wolfe Fine; Ken Matsuda, both of Stamford; James Mitchell Photis, Ridgefield, all of Conn.

Assignee: American Cyanamid Company,

Stamford, Conn. Filed: March 13,1970

Appl. No.: 19,468

US. Cl ..260/56l N, 260/558 R, 260/561 R Int. Cl ..C07c 103/08 Field of Search ..260/56l N, 561 R [56] References Cited UNITED STATES PATENTS 3,366,639 1/1968 I-laefele ..260/56l X 3,329,715 7/1967 Strohmeyer et al. ..260/5 61 Primary Examiner-Lewis Gotts Assistant Examiner-Ethel G. Love Attorney-Gordon L. Hart [5 7] ABSTRACT e.g. in aqueous solution of l-lNO or HCl at pH below 3.0. The product is the amide, e.g. acrylamide.

6 Claims, No Drawings CATALYTIC HYDRATION F NITRILES The invention relates to catalytic hydration of nitriles with water; 7

U.S. Pat. No. 3,366,639 patented Jan. 30, 1968 describes catalytic hydration of nitriles with water in the presence of manganese dioxide catalyst.

An object of the present invention is to provide improvements in the catalytic hydration of nitrile with water'using manganese dioxide catalyst.

In accordance with the invention, nitriles are hydrated with water in the presence of manganese dioxide catalyst using a dilute aqueous solution of a strong acid, preferably sufficient to lower pH of the reaction medium to 3.0 or below. At acid pH values the percent conversion of acrylonitrile to acrylamide is increased and the catalyst retains its activity for a much longer time. 1

By the term strong acid is meant an acid that is completely dissociated in dilute aqueous. solution. Suitable strongacids include inorganic and organic acids such as hydrochloric, nitric, trifluoroacetic, perchloric, benzene sulfonic, and p-toluene sulfonic acids and the like.

EXAMPLE 1 Place 1 gm. MnO, in a small test tube, then add gms. water which has been adjusted to pH 1.0 by addition of nitric acid. Dissolve 0.3 gm. acrylonitrile in the acid solution, seal the tube and react for one, hour in a constant temperature bath at 57 C. with constant agitation by rocking. At the end of one hour, analysis of a sample from the tube shows 26.7 percent conversion of the nitrile to acrylamide. A control reaction is run exactly the same, except without addition of acid, at autogenous pH about 6.8. Analysis of the control at the end of one hour shows only 12.4 percent conversion of the nitrile to acrylamide.

The acid reaction medium improves catalyst life so that high conversion and selectivity are maintained over a much longer-period, as demonstrated by the following example. I

EXA PLE:

tion and recharging steps, then react for another hour.

Percent conversion to acrylamide in the pH 1 acid soluconversion andwill not decrease substantially with continued-use .in acid medium.

To obtain the highest yield in the earlier reactions one maypretreat the manganese dioxide catalyst with acid to improve yields on the initial runs.

EXAMPLE 3 yields of both the test and control samplesin a test conducted as in Example 2.

Percent Conversion Using Pretreated Catalyst Acid Solute None HCl l-lCl pH 7 I About 7.0 1.0 1.0 Catalyst pretreated pretreated untreated run 1 30.1 24.0 9.2 2, 18.6 21.2 v 23.6 3 11.3 22.4 25.2 4 6.7 20.2 32.2 5 6.1 18.6 32.5 6 23.0

tions were, respectively, 17.8 percent, 21.6 percent and 25.4 percent for the three successive runs. The control runs at about pH 7 yielded percent conversions of 12.9 percent, 1 1.8 percent and 9.1 percent respectively. These results demonstrate the better sustained catalyst activity as well as improved conversion obtained in the acid medium. The catalyst activity (hence the percent conversion) in acid medium is improved as catalyst use time is extended. After several additional one-hour runs in acid medium the activity will level off at a good Synthox The improved catalyst activity obtained by acid pretreatment remains high through continued succeslisted below. Example 3 used the SEDEMA manganese dioxide listed below. The improvement of the invention,however, is also obtained with several other types of manganese dioxide of varying catalyst activity as indicated in the list below. Other manganese dioxides not listed will be found to be suitable for catalyst. Catalytic Manganese Dioxides A gamma form obtained from File: Wonder Company, I France Delta form obtained from Winthrop Chemical Company, U.S.A. Gamma form obtained from SEDEMAS Mechema, Belgium Delta form obtained from British Drug House, London Obtained from American Potash Corporation, U.S.A.

Winthrop SEDEMA BDl-l American Potash Electrolytic Lavinore "A" Obtained from Lavino &

Company, U.S.A. Chemical Ore No.39 Hydrated delta form obtained from General Metallic Oxides Company, U.S.A.

Sustained catalyst activity and improved conversion are obtained in a process of the invention, preferably with aqueous solutions having pH below about pH 3.0. The optimum pH value for highest yield and sustained catalyst activity is about pH 1.0, although the optimum pH value may vary depending on the selected catalyst and reaction conditions. With some kinds of manganese dioxide catalyst it may be preferable to operate at pH value higher than the optimum value to reduce loss of catalyst by dissolution in the acid solution; such loss to solution .may become severe at the lower pH values.

The hydration processis most economically carried out at ambient pressures, but the invention can be appliedto processes using pressures above or below atmospheric. Preferred reaction temperatures are in the range from about 20 to 100 Cfib'ut the invention can be applied to processes operated at higher or lower temperatures. The invention can be carried out in heterogeneous mixtures in cases where the selected nitrile is not entirely'soluble in the aqueous acid solution.

The improved yield and, extended catalyst life obtained by a process according to the invention are also tion'of catalyst produces a higher rate of reaction.

The concentration in the reactor of nitrile with respect to water is not critical; generally better yields are obtained with-a generous excess of water above the stoichiometric amount, and with enough water to dissolve the nitrile. In the hydration of'acrylonitrile we prefer to operate at or above the saturation concentration of acrylonitrile in aqueous solution. The acrylamide product is readily soluble in the aqueous reaction medium.

At pH values much'below 0.8 the loss of nitrile to side reactions may become undesirable, although the conversion and catalyst life are not seriously impaired.

In the pH range from about pH 0.8 to about pH 8.0 the selectivity of conversion'of acrylonitrile to acrylamide is near percent.

Weclaim:

1. In a process comprising hydration of a nitrile with water in the presence of manganese dioxide catalyst to.

produce an amide, the improvement wherein said ganese dioxide. catalyst is gamma-form' manganesedioxide.

5. A process defined by claim 1 wherein said nitrile is acr lonitrile.

6 A process defined by claim 1 wherein pH of said aqueous-solution is about 1.0.

a: s a: =r 

2. A process comprising pretreating catalytic manganese dioxide with aqueous solution of a strong acid and using such pretreated catalytic manganese dioxide as the catalyst in a process defined by claim
 1. 3. A process defined by claim 1 wherein said manganese dioxide catalyst is delta form manganese dioxide.
 4. A process defined by claim 1 wherein said manganese dioxide catalyst is gamma form manganese dioxide.
 5. A process defined by claim 1 wherein said nitrile is acrylonitrile.
 6. A process defined by claim 1 wherein pH of said aqueous solution is about 1.0. 